Detergent formulations

ABSTRACT

To obviate eutrophication of water, nonphosphorus detergent builders are provided. These are the water-soluble salts of N,N,di(carboxymethyl)-aspartic acid (e.g., the tetrasodium salt thereof). Conventional detergent actives may be used with these builders. Synthesis of the builders is described.

United States Patent Yang [4 1 Jan. 25, 1972 [54] DETERGENT FORMULATIONS[72] Inventor: Meiling T. Yang, Baton Rouge, La.

[73] Assignee: Ethyl Corporation, New York, NY.

[22] Filed: May 19, 1969 2 l] Appl. No: 825,984

[52] U.S.Cl ..252/527, 252/546, 26 )/534 [51] Int. Cl. ..Clld 3/30 [58]Field ol'Search ..252/137, 152; 260/534, 534C,

[56] References Cited UNITED STATES PATENTS 3,346,873 10/1967 Herrmann..252/152 X Primary Examiner-Leon D. Rosdol Assistant Examiner-M. HalpemAttorney-Donald L. Johnson [5 7] ABSTRACT 10 Claims, No DrawingsDETERGENT FORMULATIONS This invention relates to novel nonphosphorusbuilders for use with synthetic detergents and to the resultant washingcompositions and their uses.

BACKGROUND In the manufacture of detergent formulations for launderingand general purpose washing operations, it is common practice to employdetergent builderssubstances used in combination with surface-activecompounds to aid in cleansing the articles being washed. Thepolyphosphates, notably sodium tripolyphosphate and tetrasodiumpyrophosphate, are the commonly used detergent builders. However, thesematerials possess certain shortcomings. in the first place, thepolyphosphates are susceptible to hydrolysis and degradation in aqueoussolutions (Canadian Patent 737,422). In addition, the phosphorusresidues resulting from the widespread use of synthetic detergentformulations containing these phosphorus-containing builders have beensaid to contribute to eutrophication of rivers, lakes, undergroundstreams, and other bodies of water. [Detergent Phosphorus Effect onAlgae" by Thomas E. Maloney, Journal of the Water Pollution ControlFederation, Vol. 38, No. 1, pp. 3845 Jan. 1966)].

To appreciate the magnitude of the problem, it has been estimated thatover two billion pounds of salts of condensed phosphates are used indetergents each year in the United States. The phosphorus-containingbuilders can therefore be properly termed ubiquitous.

The desirability of providing an efficacious detergent builder whichdoes not suffer from the foregoing limitations is deemed to beself-evident.

Accordingly, an object of this invention is to provide efiicaciousdetergent builder systems which are hydrolytically stable and devoid ofthe eutrophic characteristics exhibited by the polyphosphates and otherphosphorus builders. Another object is to provide washing compositionswhich are devoid of phosphorus-containing builders but which possess theadvantageous characteristics of washing compositions which presentlycontain the polyphosphate builders.

Other important objects of this invention will become apparent from theensuing description and appended claims.

THE lNVENTlON In accordance with this invention it has been foundpossible to reduceindeed, eliminate-the phosphorus-containing buildersin detergent formulations without sacrifice of cleaning power andbrightness by employing as a detergent builder a water-soluble salt ofN,N-di(carboxymethyl)-aspartic acid. This acid has the formula:

CHzCOOH CH 0 OH 110 0C CH:NCHgC OOH The preferred salts are the alkalimetal salts with potassium and especially sodium being particularlypreferred. Other suitable salts include the ammonium and substitutedammonium salts.

An embodiment of this invention involves the provision, as newcompounds, of N,N-di(carboxymethyl)-aspartic acid and the water-solublesalts thereof, the sodium and potassium salts being preferred. Anotherembodiment is a process for producing such compounds.

The builders of this invention may be prepared by reacting an alkalimetal salt of nitrilodiacetic acid with an alkali metal salt of amonohalosuccinic acid in an alkaline aqueous system:

CHzCOOM GHzCOOM CHXCOOM IIN MOH CHCOOM MX CHaCOOM CHZCOOM N(CH COOM)2 Mivi tsra tiasr 9 5? PISYQFEP! 9 1 PM? I) 7 For best results, the reactionis conducted at mildly elevated temperatures (e.g., 6090 C., preferably75 C.) using alkali metal hydroxide in amount sufficient to keep thereaction solution alkaline but insufficient to cause the pH to exceed10. Treatment of the resultant organic acid salt with mineral acid(e.g., HCl) or acidic ion-exchange resin liberates the free acid.

The builders of this invention can be advantageously used with a widevariety of detergent actives or surfactants, including those known inthe art as anionic, cationic, nonionic, ampholytic, and Zwitterionicdetergents as well as any suitable mixture of such detergents. When theresultant washing compositions are used in aqueous washing systems, thecleaning power of the formulation is enhanced in much the same way aswhen the commonly used polyphosphate builders are employed. Yet thepresent builder systems are more resistant to hydrolytic degradationthan the polyphosphates and do not contribute to the eutrophicationproblems characteristic of phosphorus-containing builders.

Accordingly, this invention provides, inter alia, a washing compositioncomposed of an organic detergent surfactant suitable for use in waterand, as a builder, a water-soluble salt ofN,N-di-(carboxymethyl)-aspartic acid. Although the proportions may bevaried to suit the needs of the occasion, the weight ratio of thedetergent surfactant to the builder of this invention will normally fallwithin the range of about 1:10 to about 3:1. The preferred ratios arewithin the range of about 1:5 to about 3:2.

As noted above, the builder of this invention is generally employed inthe form of a water-soluble salt, notably an alkali metal salt, anammonium salt, or an alkyl ammonium salt. The alkali metal salts caninvolve one or a mixture of alkali metal salts although the potassium orsodium salts, especially the tetrasodium salt ofN,N-di-(carboxymethyl)-aspartic acid, are preferred because of theirrelatively low cost and enhanced effectiveness. Because the detergentformulations are generally used in alkaline aqueous systems, it isentirely feasible to use in their manufacture eitherN,N-di-(carboxymethyl)-aspartic acid itself or the partially neutralizedfree acid. The free acid group(s) will be converted to the appropriate.salt at least as soon as the formulations are put to use in an alkalineenvironment.

For best results, the formulations of this invention will provide inaqueous solution a pH between about 8 and about l2.

As noted above, the builders of this invention can be used with a widevariety of detergents including those classed in the art as anionicdetergents, cationic detergents, nonionic detergents, ampholytic (i.e.,amphoteric) detergents, and Zwitterionic detergents, and any suitablemixture of two or more of these (whether from the same class or fromdifferent classes). The anionic surface-active compounds are generallydescribed as compounds which contain hydrophilic and lyophilic groups intheir molecular structure and which ionize in an aqueous medium to giveanions containing the lyophilic group. Typical of these compounds arethe alkali metal salts of organic sulfonates or sulfates, such as thealkali metal alkyl aryl sulfonates and the alkali metal salts ofsulfates of straight chain primary alcohols. Sodium dodecylbenzenesulfonate and sodium lauryl sulfate are typical examples of theseanionic surface-active compounds (anionic synthetic detergents). For afurther amplification of anionic organic detergents which can besuccessfully built in accordance with this invention, reference shouldbe had to US. Pat. No. 3,422,021, particularly the passage extendingfrom column I l, line 47 through column 12, line 15, including thereferences therein cited, which passage is incorporated herein as iffully set out in this specification.

The cationic detergents are those which ionize in an aqueous medium togive cations containing the lyophilic group. Typical of these compoundsare the quaternary ammonium salts which contain an alkyl group of about12 to about 18 carbon atoms, such as lauryl benzyl dimethyl ammoniumchloride. Compounds of this nature are used in detergent formulationsfor special purposes, e.g., sanitizing and fabric softening.

Nonionic surface-active compounds are generally described as compoundswhich do not ionize in water solution. Oftentimes these possesshydrophilic characteristics by virtue of the presence therein of anoxygenated chain (e.g., a polyoxyethylene chain), the lyophilic portionof the molecule being derived from fatty acids, phenols, alcohols,amides or amines. Exemplary materials are the poly-(ethylene oxide)condensates of alkyl phenols (e.g., the condensation product formed fromone mole of nonyl phenol and ten moles of ethylene oxide), and thecondensation products of aliphatic alcohols and ethylene oxide (e.g.,the condensation product formed from 1 mole of tridecanol and 12 molesof ethylene oxide). Reference should be had to U.S. Pat. No. 3,422,021,especially the passage extending from column l2, line 16 through column13, line 26 where a fairly extensive discussion and exemplification ofnonionic synthetic detergents is set forth. Inasmuch as the nonionicsynthetic detergents set forth in that passage can be successfully builtin accordance with this invention, the foregoing passage is incorporatedherein as if fully set out in this specification.

The ampholytic surfactants are compounds having both anionic andcationic groups in the same molecule. Exemplary of such materials arederivatives of aliphatic amines which contain a long chain of abouteight to about 18 carbon atoms and an anionic water solubilizing group,e.g., carboxysulfo, sulfo or sulfato. Examples of ampholytic detergentsare sodium-3-dodecylamino-propionate, sodium-3- dodecylaminopropanesulfonate, sodium N-methyl taurate, and related substances such ashigher alkyl disubstituted amino acids, betaines, thetines, sulfatedlong chain olefinic amines, and sulfated imidazoline derivatives.

Zwitterionic synthetic detergents are generally regarded as derivativesof aliphatic quaternary ammonium compounds, in which the aliphaticradical may be straight chain or branched and wherein one of thealiphatic substituents contains from about 8 to l8 carbon atoms and onecontains an anionic water-solubilizing group, e.g., carboxy, sulfo, orsulfato. Examples of compounds falling within this definition are3-(N,N- dimethyl-N-hexadecylammonio)-propane-l-sulfonate and 3-(N,N-dimethyl-N-hexadecylammonio)-2-hydroxypropane-lsulfonate. For astill further appreciation of surface-active compounds (syntheticdetergents) which can be employed in the practice of this inventionreference may be had, for example, to the disclosures of U.S. Pat. No.2,961,409 and French Patent l,398,753.

The detergent builders of this invention have been found to performexceedingly well with anionic surface-active compounds and thereforethis constitutes a preferred embodiment of the invention.

Another preferred embodiment of this invention is a washing compositioncomprising an organic detergent surfactant, a water-soluble monovalentsalt of N,N-di-(carboxymethyl)- aspartic acid as a builder, and about 2to about l percent by weight based on the total weight of thecomposition of a water-soluble alkali metal silicate. The cleaningefficacy of these preferred compositions is at least comparable tocommercially available household and laundry formulations. Moreover, thesoluble silicates of such alkali metals as sodium and potassium serve aseffective corrosion inhibitors. In accordance with this preferredembodiment it is desirable to employ one or more silicates of sodium orpotassium, or both, wherein the weight ratio of SiO :M O (M=Na or K) isin the range of from about lzl to about 2.8:l. Sodium silicates whereinthis ratio is in the range of about l.6:l to about 2.5:1 are especiallyuseful because of their low cost and effectiveness.

Another preferred embodiment of this invention involves including withthe mixture of the organic detergent surfactant and theN,N-di-(carboxymethyl)-aspartic acid builder (e.g., the tetrasodiumsalt, the tetrapotassium salt, or the mixed sodium-potassium saltsthereof) an alkali metal sulfate,

preferably sodium sulfate, or an alkali metal carbonate, preferablysodium carbonate, or both. Amounts up to about 60 percent by weight ofthe total formulation are suitable. These formulations are effective,economical mainstays of finished detergent formulations for laundry,household and/or industrial use. In the preferred compositions theamount of alkali metal sulfate and/or alkali metal carbonate isgenerally from about 10 to about 50 percent by weight based on the totalweight of the formulation.

Finished detergent formulations of this invention may contain minoramounts of other commonly used materials in order to enhance theeffectiveness or attractiveness of the product. Exemplary of suchmaterials are soluble sodium carboxymethyl cellulose or other soilredeposition inhibitors; benzotriazole, ethylene thiourea, or othertarnish inhibitors; perfume; fluorescers; dyes or pigments; brighteningagents; enzymes; water; alcohols; other builder additives, such as thewater-soluble salts of ethylenediaminetetraacetic acid, N-(2-hydroxyethyl)-ethylenediaminetriacetic acid, nitrilotriacetic acid andN-(2-hydroxyethyl)-nitrilodiacetic acid; and pH adjusters, such assodium hydroxide and potassium hydroxide. In the built liquid detergentformulations of this invention, the use of hydrotropic agents may befound efficacious Suitable hydrotropes include the water-soluble alkalimetal salts of toluene sulfonic acid, benzene sulfonic acid, and xylenesulfonic acid. Potassium toluene sulfonate and sodium toluene sulfonateare preferred for this use and will normally be employed in concentratesranging up to about 10 or 12 percent by weight based on the totalcomposition.

It will be apparent from the foregoing that the compositions of thisinvention may be formulated according to any of the various commerciallydesirable forms. For example, the formulations of this invention may beprovided in granular form, in liquid form, in tablet form, or in theform of flakes or powders.

The relative proportions and absolute quantities of the severalingredients of the finished compositions of this invention aresusceptible to variation and in most cases will vary depending upon suchfactors as the nature of the particular ingredients being utilized, theend use for which the composition is intended to be put, the relativecosts of the ingredients, and the like. For example, the totalconcentration of the detergent formulations of this invention in waterwill normally range below about 0.3 percent by weight although it isentirely feasible to utilize higher concentrations where thecircumstances warrant or justify the use of higher concentrations. Inmost cases the aqueous washing solutions of this invention will containfrom about 0.05 to about 0.25 weight percent of combined detergentactive(s) and builder. The preferred compositions of this invention arephosphorus free although it may be desired to include therein reducedquantities of conventional phosphorus-containing materials such assodium tripolyphosphate, tetrasodium pyrophosphate, salts of substitutedmethylene diphosphonic acids, long chain tertiary phosphine oxides, orthe like.

The invention is not to be limited to any particular method of mixingthe builder and the detergent. The builder may be mechanically mixed in,crutched in the detergent in the form of a slurry, or dissolved in asolution of the detergent. In addition, the builder system may beadmixed with the detergent in any of the forms in which the detergent ismanufactured, as well as being added simultaneously or separately to anaqueous solution. In any event, the present builder system is intendedto be used with the detergent at the time of application as a cleansingagent.

in order to still further illustrate the practice of this invention, thefollowing examples are presented.

EXAMPLE I Disodium nitrilodiacetate, HN(CH COONa) H O, 20 grams (0.1mole), was dissolved in 50 ml. of water in a 500 ml. three-necked flaskequipped with a mechanical stirrer, a combination pH electrode and adropping funnel. Bromosuccinic acid, 20 grams (0.1 mole), wasneutralized with 8 grams of NaOH in 100 ml. of water and the resultingsolution was added to the flask. While the flask .was immersed in an oilbath at 70 C., 4 grams of NaOH in 50 ml. of water was added dropwise atsuch a rate that the pH of the reaction mixture always remained below10. The mixture was stirred for 2 more hours.

The reaction mixture was concentrated to 50 ml. at 70 C. After cooling,150 ml. of methanol was added. The taffylike material was separated andblended with four 100 ml. portions of methanol. The solid thus obtainedstill showed positive bromide test. It was dissolved in 50 ml. of waterand passed through a 2.5 O cm. column of an ion-exchange resin (Dowex50W-X1, 50/100 mesh), the resin initially being in the acid form. Waterwas used as the eluent and the following acidic effluent fractions werecollected and evaporated;

Residue Fractions Volume pH of fraction After evaporation I 125 ml. 2.5Trace, brownish 2 125 1.5-2.0 Trace, brownish 3 225 l 12 g., light green4 225 2.5-4 None 5 300 4.0-4.5 Trace 7 100 4 None EXAMPLE I] A preferredbuilt formulation of this invention had the following composition:

Weight percent Dodecylbenzene sulfonate (a typical linear alkyl benzenesulfonate 20.0 Sodium silicate (ratio SiO,:Na,O

of 2.4:1 6.0 Sodium carboxymethyl cellulose 0.6 Sodium sulfate 33.4

Tetrasodium salt of N,N-di- (carboxymethyl)-aspartic acid 400 Theperformance of this detergent composition was evaluated by use of thestandard Launder-Ometer test. In particular, the formulation wasdissolved in water to a concentration of 0.15 weight percent and the pHof the solution adjusted to 9.5 with small amounts of sodium hydroxidesolution. The water had a hardness of 150 p.p.m. (Ca/Mg 3/2). Swatchesof standard artificially soiled cloth were subjected to the washingprocedure. The LaunderOmeter bath temperature was fixed at 120 F. andthe washing span was 10 minutes. After washing, the samples were removedfrom the washing solution and thoroughly rinsed with pure water. Afterdrying, the whiteness of the cloths was ascertained by use of a standardcommercially available reflectance photometer. The identical procedurealso was employed with a formulation identical to that described abovewith the exception that sodium tripolyphosphate was used in lieu of thetetrasodium salt of N,N-di-(carboxymethyl)-aspartic acid.

In these tests it was established that the formulation of this inventionwas as effective as the corresponding sodium tripolyphosphateformulation. in particular, the cloths washed with the formulation ofthis invention had a whiteness of 105 as compared to the whiteness ofthe same kind of soiled clothes washed in the sodium tripolyphosphateformulation (assigned the value of 100 percent).

EXAMPLE 111 Some illustrative solid heavy duty laundering formulationsof this invention are as follows (percentages being weight percentages):

Surfaceactive agent (See note 1 10-1251: Tetrasodium salt of N,N-di-(carboxymethyH-aspartic acid l0-25% Sodium metasilicate (anhydrous) 2l0%Sodium carboxymethyl cellulose 1% Optical brightener (fluorescent dye)0. l 911 Perfume 0.1%

Sodium sulfate (See note 2) Balance to One or a combination of thefollowing: sodium alkyl aryl sulfonate, sodium alkyl sulfonate, sodiumalkane sulfonate, sodium alkenyl sulfonate, octyl phenol ethoxylate.nonyl phenol ethoxylate, fatty alcohol ethoxylate, fatty acid amide.alkanol amide, tall oil ethoxylate.

The sodium sulfate may be totally or partially replaced by one or moreufthe fol lowing: borax, soda ash, sodium bicarbonate. sodium chloride,sodium sesquicarbonate.

EXAMPLE 1V Typical liquid laundering formulations of this invention areas follows (percentages being weight percentages):

Surface-active agent (See note 1 above) 10-15% Tetrasodium salt ofN,N-di (carboxymethyD-aspartic acid (See note 3) l020% Potassiummetasilicate 2l0% Sodium carboxymethyl cellulose 1% Sodium benzenesulfonate (See note 4) 5-l0% Optical brightener (fluorescent dye) 0l%Water Balance to 100% The tetrasodium saltN,N-di(carboxymethyl)-aspartic acid may be totally or partially replacedby the tetrapotassium salt ofN,Ndi-(carboxymethyl)-aspartic acid.

The sodium benzene sulfonate may be totally or partially replaced bypotassium benzene sulfonate, sodium toluene sulfonate, sodium xylenesulfonate, etc.

it is not intended that this invention be unduly limited by theexemplifications herein provided.

Besides being effective detergent builders,N,N-di-(carboxymethyl)-aspartic acid and its water-soluble salts arehighly effective sequesterants for calcium in aqueous systems.

lclaim:

l. A washing composition consisting essentially of an organic detergentsurfactant selected from the group consisting of anionic detergents,cationic detergents, nonionic detergents, ampholytic detergents,zwitterionic detergents, and mixtures of the above suitable for use inwater and, as a builder, a water-soluble salt ofN,N-di-(carboxymethyl)-aspartic acid selected from the group consistingof alkali metal salts, ammonium salts, and alkyl ammonium salts, theratio by weight of the detergent surfactant to the builder being in therange of about 1:10 to about 3: l.

2. The composition of claim 1 wherein said water-soluble salt is asodium salt.

3. The composition of claim 1 wherein said detergent surfactant is oneor a mixture of anionic detergents.

4. The composition of claim 1 additionally containing from about 2 toabout 10 percent by weight based on the total weight of the compositionof a water-soluble alkali metal silicate.

5. The composition of claim 1 additionally containing up to about 60percent by weight based on the total weight of the composition of analkali metal sulfate or an alkali metal carbonate, or both.

6. The composition of claim 1 wherein said detergent surfactant is oneor a mixture of anionic detergents, wherein said salt is the tetrasodiumsalt of N,N-di-(carboxymethyU-aspartic acid, and wherein the compositionadditionally contains from about 2 to about 10 percent by weight basedon the total weight of the composition of a water-soluble sodiumsilicate and from about 10 to about 50 percent by weight based on thetotal weight of the composition of sodium sulfate.

about 1:10 to about 3: I, said system having a pH between about 8 andabout 12.

8. The method of washing articles which comprises contacting the samewith an aqueous washing system of claim 7.

9. The composition of claim 7 wherein said detergent surfactant is oneor a mixture of anionic detergents.

10. The composition of claim 7 wherein said water-soluble salt is asodium salt of N,N-di-(carboxymethyl)-aspartic acid.

2. The composition of claim 1 wherein said water-soluble salt is asodium salt.
 3. The composition of claim 1 wherein said detergentsurfactant is one or a mixture of anionic detergents.
 4. The compositionof claim 1 additionally containing from about 2 to about 10 percent byweight based on the total weight of the composition of a water-solublealkali metal silicate.
 5. The composition of claim 1 additionallycontaining up to about 60 percent by weight based on the total weight ofthe composition of an alkali metal sulfate or an alkali metal carbonate,or both.
 6. The composition of claim 1 wherein said detergent surfactantis one or a mixture of anionic detergents, wherein said salt is thetetrasodium salt of N,N-di-(carboxymethyl)-aspartic acid, and whereinthe composition additionally contains from about 2 to about 10 percentby weight based on the total weight of the composition of awater-soluble sodium silicate and from about 10 to about 50 percent byweight based on the total weight of the composition of sodium sulfate.7. An aqueous washing system consisting essentially of water, an organicdetergent surfactant selected from the group consisting of anionicdetergents, cationic detergents, nonionic detergents, ampholyticdetergents, zwitterionic detergents, and mixtures of the above and, as abuilder therefor, a water-soluble salt of N,N-di-(carboxymethyl)-aspartic acid selected from the group consisting ofalkali metal salts, ammonium salts, and alkyl ammonium salts, the ratioby weight of said detergent surfactant to said builder being in therange of from about 1:10 to about 3: 1, said system having a pH betweenabout 8 and about
 12. 8. The method of washing articles which comprisescontacting the same with an aqueous washing system of claim
 7. 9. Thecomposition of claim 7 wherein said detergent surfactant is one or amixture of anionic detergents.
 10. The composition of claim 7 whereinsaid water-soluble salt is a sodium salt ofN,N-di-(carboxymethyl)-aspartic acid.